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 * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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 */

package javax.sound.midi;

/**
 * A <code>ShortMessage</code> contains a MIDI message that has at most
 * two data bytes following its status byte.  The types of MIDI message
 * that satisfy this criterion are channel voice, channel mode, system common,
 * and system real-time--in other words, everything except system exclusive
 * and meta-events.  The <code>ShortMessage</code> class provides methods
 * for getting and setting the contents of the MIDI message.
 * <p>
 * A number of <code>ShortMessage</code> methods have integer parameters by which
 * you specify a MIDI status or data byte.  If you know the numeric value, you
 * can express it directly.  For system common and system real-time messages,
 * you can often use the corresponding fields of <code>ShortMessage</code>, such as
 * {@link #SYSTEM_RESET SYSTEM_RESET}.  For channel messages,
 * the upper four bits of the status byte are specified by a command value and
 * the lower four bits are specified by a MIDI channel number. To
 * convert incoming MIDI data bytes that are in the form of Java's signed bytes,
 * you can use the <A HREF="MidiMessage.html#integersVsBytes">conversion code</A>
 * given in the <code>{@link MidiMessage}</code> class description.
 *
 * @author David Rivas
 * @author Kara Kytle
 * @author Florian Bomers
 * @see SysexMessage
 * @see MetaMessage
 */

public class ShortMessage extends MidiMessage {

  // Status byte defines

  // System common messages

  /**
   * Status byte for MIDI Time Code Quarter Frame message (0xF1, or 241).
   *
   * @see MidiMessage#getStatus
   */
  public static final int MIDI_TIME_CODE = 0xF1; // 241

  /**
   * Status byte for Song Position Pointer message (0xF2, or 242).
   *
   * @see MidiMessage#getStatus
   */
  public static final int SONG_POSITION_POINTER = 0xF2; // 242

  /**
   * Status byte for MIDI Song Select message (0xF3, or 243).
   *
   * @see MidiMessage#getStatus
   */
  public static final int SONG_SELECT = 0xF3; // 243

  /**
   * Status byte for Tune Request message (0xF6, or 246).
   *
   * @see MidiMessage#getStatus
   */
  public static final int TUNE_REQUEST = 0xF6; // 246

  /**
   * Status byte for End of System Exclusive message (0xF7, or 247).
   *
   * @see MidiMessage#getStatus
   */
  public static final int END_OF_EXCLUSIVE = 0xF7; // 247

  // System real-time messages

  /**
   * Status byte for Timing Clock message (0xF8, or 248).
   *
   * @see MidiMessage#getStatus
   */
  public static final int TIMING_CLOCK = 0xF8; // 248

  /**
   * Status byte for Start message (0xFA, or 250).
   *
   * @see MidiMessage#getStatus
   */
  public static final int START = 0xFA; // 250

  /**
   * Status byte for Continue message (0xFB, or 251).
   *
   * @see MidiMessage#getStatus
   */
  public static final int CONTINUE = 0xFB; // 251

  /**
   * Status byte for Stop message (0xFC, or 252).
   *
   * @see MidiMessage#getStatus
   */
  public static final int STOP = 0xFC; //252

  /**
   * Status byte for Active Sensing message (0xFE, or 254).
   *
   * @see MidiMessage#getStatus
   */
  public static final int ACTIVE_SENSING = 0xFE; // 254

  /**
   * Status byte for System Reset message (0xFF, or 255).
   *
   * @see MidiMessage#getStatus
   */
  public static final int SYSTEM_RESET = 0xFF; // 255

  // Channel voice message upper nibble defines

  /**
   * Command value for Note Off message (0x80, or 128)
   */
  public static final int NOTE_OFF = 0x80;  // 128

  /**
   * Command value for Note On message (0x90, or 144)
   */
  public static final int NOTE_ON = 0x90;  // 144

  /**
   * Command value for Polyphonic Key Pressure (Aftertouch) message (0xA0, or 160)
   */
  public static final int POLY_PRESSURE = 0xA0;  // 160

  /**
   * Command value for Control Change message (0xB0, or 176)
   */
  public static final int CONTROL_CHANGE = 0xB0;  // 176

  /**
   * Command value for Program Change message (0xC0, or 192)
   */
  public static final int PROGRAM_CHANGE = 0xC0;  // 192

  /**
   * Command value for Channel Pressure (Aftertouch) message (0xD0, or 208)
   */
  public static final int CHANNEL_PRESSURE = 0xD0;  // 208

  /**
   * Command value for Pitch Bend message (0xE0, or 224)
   */
  public static final int PITCH_BEND = 0xE0;  // 224

  // Instance variables

  /**
   * Constructs a new <code>ShortMessage</code>.  The
   * contents of the new message are guaranteed to specify
   * a valid MIDI message.  Subsequently, you may set the
   * contents of the message using one of the <code>setMessage</code>
   * methods.
   *
   * @see #setMessage
   */
  public ShortMessage() {
    this(new byte[3]);
    // Default message data: NOTE_ON on Channel 0 with max volume
    data[0] = (byte) (NOTE_ON & 0xFF);
    data[1] = (byte) 64;
    data[2] = (byte) 127;
    length = 3;
  }

  /**
   * Constructs a new {@code ShortMessage} which represents a MIDI
   * message that takes no data bytes.
   * The contents of the message can be changed by using one of
   * the {@code setMessage} methods.
   *
   * @param status the MIDI status byte
   * @throws InvalidMidiDataException if {@code status} does not specify a valid MIDI status byte
   * for a message that requires no data bytes
   * @see #setMessage(int)
   * @see #setMessage(int, int, int)
   * @see #setMessage(int, int, int, int)
   * @see #getStatus()
   * @since 1.7
   */
  public ShortMessage(int status) throws InvalidMidiDataException {
    super(null);
    setMessage(status); // can throw InvalidMidiDataException
  }

  /**
   * Constructs a new {@code ShortMessage} which represents a MIDI message
   * that takes up to two data bytes. If the message only takes one data byte,
   * the second data byte is ignored. If the message does not take
   * any data bytes, both data bytes are ignored.
   * The contents of the message can be changed by using one of
   * the {@code setMessage} methods.
   *
   * @param status the MIDI status byte
   * @param data1 the first data byte
   * @param data2 the second data byte
   * @throws InvalidMidiDataException if the status byte or all data bytes belonging to the message
   * do not specify a valid MIDI message
   * @see #setMessage(int)
   * @see #setMessage(int, int, int)
   * @see #setMessage(int, int, int, int)
   * @see #getStatus()
   * @see #getData1()
   * @see #getData2()
   * @since 1.7
   */
  public ShortMessage(int status, int data1, int data2)
      throws InvalidMidiDataException {
    super(null);
    setMessage(status, data1, data2); // can throw InvalidMidiDataException
  }

  /**
   * Constructs a new {@code ShortMessage} which represents a channel
   * MIDI message that takes up to two data bytes. If the message only takes
   * one data byte, the second data byte is ignored. If the message does not
   * take any data bytes, both data bytes are ignored.
   * The contents of the message can be changed by using one of
   * the {@code setMessage} methods.
   *
   * @param command the MIDI command represented by this message
   * @param channel the channel associated with the message
   * @param data1 the first data byte
   * @param data2 the second data byte
   * @throws InvalidMidiDataException if the command value, channel value or all data bytes
   * belonging to the message do not specify a valid MIDI message
   * @see #setMessage(int)
   * @see #setMessage(int, int, int)
   * @see #setMessage(int, int, int, int)
   * @see #getCommand()
   * @see #getChannel()
   * @see #getData1()
   * @see #getData2()
   * @since 1.7
   */
  public ShortMessage(int command, int channel, int data1, int data2)
      throws InvalidMidiDataException {
    super(null);
    setMessage(command, channel, data1, data2);
  }


  /**
   * Constructs a new <code>ShortMessage</code>.
   *
   * @param data an array of bytes containing the complete message. The message data may be changed
   * using the <code>setMessage</code> method.
   * @see #setMessage
   */
  // $$fb this should throw an Exception in case of an illegal message!
  protected ShortMessage(byte[] data) {
    // $$fb this may set an invalid message.
    // Can't correct without compromising compatibility
    super(data);
  }


  /**
   * Sets the parameters for a MIDI message that takes no data bytes.
   *
   * @param status the MIDI status byte
   * @throws InvalidMidiDataException if <code>status</code> does not specify a valid MIDI status
   * byte for a message that requires no data bytes.
   * @see #setMessage(int, int, int)
   * @see #setMessage(int, int, int, int)
   */
  public void setMessage(int status) throws InvalidMidiDataException {
    // check for valid values
    int dataLength = getDataLength(status); // can throw InvalidMidiDataException
    if (dataLength != 0) {
      throw new InvalidMidiDataException(
          "Status byte; " + status + " requires " + dataLength + " data bytes");
    }
    setMessage(status, 0, 0);
  }


  /**
   * Sets the  parameters for a MIDI message that takes one or two data
   * bytes.  If the message takes only one data byte, the second data
   * byte is ignored; if the message does not take any data bytes, both
   * data bytes are ignored.
   *
   * @param status the MIDI status byte
   * @param data1 the first data byte
   * @param data2 the second data byte
   * @throws InvalidMidiDataException if the the status byte, or all data bytes belonging to the
   * message, do not specify a valid MIDI message.
   * @see #setMessage(int, int, int, int)
   * @see #setMessage(int)
   */
  public void setMessage(int status, int data1, int data2) throws InvalidMidiDataException {
    // check for valid values
    int dataLength = getDataLength(status); // can throw InvalidMidiDataException
    if (dataLength > 0) {
      if (data1 < 0 || data1 > 127) {
        throw new InvalidMidiDataException("data1 out of range: " + data1);
      }
      if (dataLength > 1) {
        if (data2 < 0 || data2 > 127) {
          throw new InvalidMidiDataException("data2 out of range: " + data2);
        }
      }
    }

    // set the length
    length = dataLength + 1;
    // re-allocate array if ShortMessage(byte[]) constructor gave array with fewer elements
    if (data == null || data.length < length) {
      data = new byte[3];
    }

    // set the data
    data[0] = (byte) (status & 0xFF);
    if (length > 1) {
      data[1] = (byte) (data1 & 0xFF);
      if (length > 2) {
        data[2] = (byte) (data2 & 0xFF);
      }
    }
  }


  /**
   * Sets the short message parameters for a  channel message
   * which takes up to two data bytes.  If the message only
   * takes one data byte, the second data byte is ignored; if
   * the message does not take any data bytes, both data bytes
   * are ignored.
   *
   * @param command the MIDI command represented by this message
   * @param channel the channel associated with the message
   * @param data1 the first data byte
   * @param data2 the second data byte
   * @throws InvalidMidiDataException if the status byte or all data bytes belonging to the message,
   * do not specify a valid MIDI message
   * @see #setMessage(int, int, int)
   * @see #setMessage(int)
   * @see #getCommand
   * @see #getChannel
   * @see #getData1
   * @see #getData2
   */
  public void setMessage(int command, int channel, int data1, int data2)
      throws InvalidMidiDataException {
    // check for valid values
    if (command >= 0xF0 || command < 0x80) {
      throw new InvalidMidiDataException("command out of range: 0x" + Integer.toHexString(command));
    }
    if ((channel & 0xFFFFFFF0) != 0) { // <=> (channel<0 || channel>15)
      throw new InvalidMidiDataException("channel out of range: " + channel);
    }
    setMessage((command & 0xF0) | (channel & 0x0F), data1, data2);
  }


  /**
   * Obtains the MIDI channel associated with this event.  This method
   * assumes that the event is a MIDI channel message; if not, the return
   * value will not be meaningful.
   *
   * @return MIDI channel associated with the message.
   * @see #setMessage(int, int, int, int)
   */
  public int getChannel() {
    // this returns 0 if an invalid message is set
    return (getStatus() & 0x0F);
  }


  /**
   * Obtains the MIDI command associated with this event.  This method
   * assumes that the event is a MIDI channel message; if not, the return
   * value will not be meaningful.
   *
   * @return the MIDI command associated with this event
   * @see #setMessage(int, int, int, int)
   */
  public int getCommand() {
    // this returns 0 if an invalid message is set
    return (getStatus() & 0xF0);
  }


  /**
   * Obtains the first data byte in the message.
   *
   * @return the value of the <code>data1</code> field
   * @see #setMessage(int, int, int)
   */
  public int getData1() {
    if (length > 1) {
      return (data[1] & 0xFF);
    }
    return 0;
  }


  /**
   * Obtains the second data byte in the message.
   *
   * @return the value of the <code>data2</code> field
   * @see #setMessage(int, int, int)
   */
  public int getData2() {
    if (length > 2) {
      return (data[2] & 0xFF);
    }
    return 0;
  }


  /**
   * Creates a new object of the same class and with the same contents
   * as this object.
   *
   * @return a clone of this instance.
   */
  public Object clone() {
    byte[] newData = new byte[length];
    System.arraycopy(data, 0, newData, 0, newData.length);

    ShortMessage msg = new ShortMessage(newData);
    return msg;
  }


  /**
   * Retrieves the number of data bytes associated with a particular
   * status byte value.
   *
   * @param status status byte value, which must represent a short MIDI message
   * @return data length in bytes (0, 1, or 2)
   * @throws InvalidMidiDataException if the <code>status</code> argument does not represent the
   * status byte for any short message
   */
  protected final int getDataLength(int status) throws InvalidMidiDataException {
    // system common and system real-time messages
    switch (status) {
      case 0xF6:                      // Tune Request
      case 0xF7:                      // EOX
        // System real-time messages
      case 0xF8:                      // Timing Clock
      case 0xF9:                      // Undefined
      case 0xFA:                      // Start
      case 0xFB:                      // Continue
      case 0xFC:                      // Stop
      case 0xFD:                      // Undefined
      case 0xFE:                      // Active Sensing
      case 0xFF:                      // System Reset
        return 0;
      case 0xF1:                      // MTC Quarter Frame
      case 0xF3:                      // Song Select
        return 1;
      case 0xF2:                      // Song Position Pointer
        return 2;
      default:
    }

    // channel voice and mode messages
    switch (status & 0xF0) {
      case 0x80:
      case 0x90:
      case 0xA0:
      case 0xB0:
      case 0xE0:
        return 2;
      case 0xC0:
      case 0xD0:
        return 1;
      default:
        throw new InvalidMidiDataException("Invalid status byte: " + status);
    }
  }
}
